Incentive mechanism design for delayed WiFi offloading

WiFi offloading helps serve ever-increasing data traffic in cellular networks and mitigate the network congestion. Yet it can only apply to cellular users within WiFi coverage. Recently, delayed WiFi offloading is proposed to exploit users' mobility to purposely travel to WiFi coverage for data offloading. Its successful implementation depends on users' willingness to delay ongoing cellular data services until entering WiFi coverage. This paper proposes an incentive mechanism to allow a network operator to optimally reward his users to participate in delayed WiFi offloading, so as to reduce the network congestion. We formulate the design problem as a two-stage Stackelberg game: in Stage I, the operator announces a uniform reward to users to delay their existing cellular services; and in Stage II, each user decides to join the delayed offloading or not, depending on the reward, the network congestion, and his estimation of waiting cost for WiFi connection. The operator and users may or may not know all users' mobility and waiting cost information; thus, we propose optimal reward mechanisms under various information availability scenarios. Interestingly, we show that the optimal reward does not always increase with the cellular traffic load, as the increased network congestion can also help motivate users to switch to WiFi networks.